This project will investigate personal models of two chronic diseases in older adults, non-insulin dependent diabetes mellitus and osteoarthritis. Building on the concept of a schema in social cognition, personal models are defined as patients' cognitive and effective representations of the cause, symptoms, course, treatment, and consequences of their illness. The specific aims of our personal-models approach are to relate the content and structure of personal models to (a) model-guided processing of illness-related information, and (b) disease-management activities and functional status. Studying personal models of two diseases will permit (cross-validation of the personal-models approach in the prediction of outcome variables in chronic disease, and (b) comparisons between the models of these two prevalent diseases of old age. Separate investigations of each disease will be conducted in parallel in a sequence of interlocking studies. Subjects in each investigation will be aged 65 and older. For each disease, in Phase 1, we will develop a structured interview that will provide multiple indicators from which to construct theoretically guided composite variables to assess key dimensions of personal models. Scores on these variables will be related to a variety of patient characteristics. Phase 2 will replicate Phase 1 using refined instruments and different samples. In addition, we will use several procedures from research in social cognition to investigate the relations between the content of personal models and the processing of illness-related information. Finally, in Phase 3, prospective studies will determine the stability of personal models and their utility for predicting disease-management activities and functional status. The long-term objectives of this project are to (1) contribute to basic theory in social cognition by studying older adults' representations of an important aspect of their everyday lives, and (2) to enhance the effectiveness of patient-education programs and patient-practitioner interactions designed to increase levels of disease-management activities and functional status.